1. Technical Field
The present invention relates to a filter or resonator; more particularly, to a tunable filter or resonator having a Fabry-Perot air gap.
2. Description of Related Art
It is known in the art to use air gap Fabry-Perot filters/resonators to provide a variety of optical functions, such as is described in U.S. Pat. No. 6,137,812 to J. T. Kringlebotn or in U.S. Pat. No. 6,181,729 to Lunt, or in U.S. Pat. No. 6,115,401 to Scobey et al., all of which are incorporated herein in their entirety.
Such Fabry-Perot filters are created by epoxying optical fibers within a tube and spacing the ends a precise distance apart. However, such filters cannot tolerate high temperature operations and do not exhibit good long-term stability. Further, they are difficult to tune. Those that are tunable are typically tuned by changing the temperature of the filter package or other similar techniques. Fabry-Perot filters tuned in such ways exhibit creep hysteresis and other fiber attachment problems.